Now I will tell you what I consider a mature account in a casino, as many people already know, many casinos have a VIP program
To summarize what I said before, a mature account in a casino is when you are in the VIP program and if you can receive weekly and monthly bonuses it is better.
You don't have mature accounts if you only register those accounts and turn to be inactively with your bet.
You must bet a lot to rank up with their VIP programs and it is not achievable for all gamblers. You must be a very careful and smart gambler to bet regularly and rank up in their VIP programs but still are able to maintain your initial capital. It is a like a stick and a carrot policy from their VIP programs.
You must do many things to have a casino matured account: register it, bet, nurture your total bet value, rank up to higher VIP levels.